Change enumerator default linkage type for C

Redeclaration lookup should never find hidden enumerators in C, because
they do not have linkage (C11 6.2.2/6)

The linkage of an enumerator should be VisibleNoLinkage, and
isHiddenDeclarationVisible should be checking hasExternalFormalLinkage.

This is was reviewed as part of D31778, but splitted into a different
commit for clarity.

rdar://problem/31909368

llvm-svn: 306917

4 files changed, 8 insertions, 3 deletions

diff --git a/clang/include/clang/Basic/Visibility.h b/clang/include/clang/Basic/Visibility.h
index 6ac52ed6b5e..cc839d789e7 100644
--- a/clang/include/clang/Basic/Visibility.h
+++ b/clang/include/clang/Basic/Visibility.h
@@ -75,6 +75,9 @@ public:
   static LinkageInfo none() {
     return LinkageInfo(NoLinkage, DefaultVisibility, false);
   }
+  static LinkageInfo visible_none() {
+    return LinkageInfo(VisibleNoLinkage, DefaultVisibility, false);
+  }
 
   Linkage getLinkage() const { return (Linkage)linkage_; }
   Visibility getVisibility() const { return (Visibility)visibility_; }
diff --git a/clang/include/clang/Sema/Lookup.h b/clang/include/clang/Sema/Lookup.h
index fc16ad2e819..ea32997d406 100644
--- a/clang/include/clang/Sema/Lookup.h
+++ b/clang/include/clang/Sema/Lookup.h
@@ -275,7 +275,7 @@ public:
   /// declarations, such as those in modules that have not yet been imported.
   bool isHiddenDeclarationVisible(NamedDecl *ND) const {
     return AllowHidden ||
-           (isForRedeclaration() && ND->isExternallyVisible());
+           (isForRedeclaration() && ND->hasExternalFormalLinkage());
   }
 
   /// Sets whether tag declarations should be hidden by non-tag
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 8677b1155a6..267c6992af8 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1251,7 +1251,9 @@ static LinkageInfo computeLVForDecl(const NamedDecl *D,
 
     case Decl::EnumConstant:
       // C++ [basic.link]p4: an enumerator has the linkage of its enumeration.
-      return getLVForDecl(cast<EnumDecl>(D->getDeclContext()), computation);
+      if (D->getASTContext().getLangOpts().CPlusPlus)
+        return getLVForDecl(cast<EnumDecl>(D->getDeclContext()), computation);
+      return LinkageInfo::visible_none();
 
     case Decl::Typedef:
     case Decl::TypeAlias:
diff --git a/clang/test/Index/linkage.c b/clang/test/Index/linkage.c
index ab006590b61..b0dcb30990a 100644
--- a/clang/test/Index/linkage.c
+++ b/clang/test/Index/linkage.c
@@ -20,7 +20,7 @@ void f16(void) {
 
 
 // CHECK: EnumDecl=Baz:3:6 (Definition)linkage=External
-// CHECK: EnumConstantDecl=Qux:3:12 (Definition)linkage=External
+// CHECK: EnumConstantDecl=Qux:3:12 (Definition)linkage=NoLinkage
 // CHECK: VarDecl=x:4:5linkage=External
 // CHECK: FunctionDecl=foo:5:6linkage=External
 // CHECK: VarDecl=w:6:12linkage=Internal